Abstract
Rapeseed meal and waste molasses are two important agro-industrial by-products which are produced in large quantities. In this study, solid state fermentation and fungal autolysis were performed to produce rapeseed meal hydrolysate (RMH) using fungal strains of Aspergillus oryzae, Penicillium oxalicum and Neurospora crassa. The hydrolysate was used as fermentation feedstock for heterotrophic growth of microalga Crypthecodinium cohnii that produce docosahexaenoic acid (DHA). The addition of waste molasses as a supplementary carbon source greatly increased the biomass and DHA yield. In the batch fermentations using media composed of diluted RMH (7%) and 1-9% waste molasses, the highest biomass concentration and DHA yield reached 3.43 g/L and 8.72 mg/L, respectively. The algal biomass produced from RMH and molasses medium also had a high percentage of DHA (22-34%) in total fatty acids similar to that of commercial algal biomass. RMH was shown to be rich in nitrogen supply comparable to the commercial nitrogen feedstock like yeast extract. Using RMH as sole nitrogen source, waste molasses excelled other carbon sources and produced the highest concentration of biomass. This study suggests that DHA production of the marine dinoflagellate C. cohnii could be greatly improved by concomitantly using the cheap by-products rapeseed meal hydrolysate and molasses as alternative feedstock.
Highlights
Introductiondocosahexaenoic acid (DHA) Production by Microalga C. cohnii Using By-Products as Feedstock replaced by renewable energy sources [1], including liquid biofuels which have the potential to decrease greenhouse gas (GHG) emissions and to meet the energy demands in the transport sector over the past decades [2,3]
With the depletion of fossil fuel reserves and the increase of greenhouse gas (GHG) emissions contributed largely by the use of fossil fuels, these unsustainable fuels are needed to be graduallyPLOS ONE | DOI:10.1371/journal.pone.0125368 May 5, 2015docosahexaenoic acid (DHA) Production by Microalga C. cohnii Using By-Products as Feedstock replaced by renewable energy sources [1], including liquid biofuels which have the potential to decrease GHG emissions and to meet the energy demands in the transport sector over the past decades [2,3]
As strain LZ01 and LZ02 are from same species with close activity, strains of LZ01, J1 and J2 were eventually selected for the throughout experiments including solid state fermentation and autolysis
Summary
DHA Production by Microalga C. cohnii Using By-Products as Feedstock replaced by renewable energy sources [1], including liquid biofuels which have the potential to decrease GHG emissions and to meet the energy demands in the transport sector over the past decades [2,3]. Production of biodiesel and cooking oils using rapeseed as feedstock had led to the generation of large quantities of rapeseed meal (RSM), a by-product of oil extraction from seeds. The global RSM production has been constantly increasing over the past years due to the growing demand for either biodiesel or edible oils, reaching an estimated production capacity of 68.41 million tons in 2014 [3,4,5]
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